Last significant post I could find on this subjected started in 2016.

I recently took an unassigned drive off my Unraid server and hooked to my Windows PC. It is formatted NTFS. I found it was 27% fragmented. Indeed, Windows had a such hard time de-fragmenting it, I ended up wiping it and copying the files manually with Krusader. I would copy so many gigs, bring it to my Windows PC, defrag it, and hook it back up to Unraid. Kept doing the process until everything was copied, about 3TB.

(I was using Rsync to copy the files previously).

Which brought me to the question, is there a solution to de-fragement these drives while attached to the Unraid NAS? Also, had me wondering about the drives in my Array itself. How fragmented are those?

For NTFS best to use WIndows defrag.

5 hours ago, RaidPC said:

I would copy so many gigs, bring it to my Windows PC, defrag it, and hook it back up to Unraid. Kept doing the process until everything was copied, about 3TB.

That makes no sense, if you wiped and copied again there would be no fragmentation then, so pointless to run defrags.

5 hours ago, RaidPC said:

Also, had me wondering about the drives in my Array itself. How fragmented are those?

Pretty much doesn't matter with the usual filesystems used in the array.

Edited April 8Apr 8 by Kilrah

"That makes no sense, if you wiped and copied again there would be no fragmentation then, so pointless to run defrags."

Can only speak on what I saw. But when files are written to a drive, unless things have changed, they are not written in a nice, neat order, from the front of the disk to the back. So when you load a lot of files as in terabytes, I would expect fragmentation. Just didn't expect coming from Rsync to Windows defrag it would be so bad for Windows to struggle with it.

Using Windows defrag as suggested above, with the process of stopping after so many gigabytes and de-fragmenting.

10 hours ago, RaidPC said:

But when files are written to a drive, unless things have changed, they are not written in a nice, neat order, from the front of the disk to the back.

You must be confused because it's how it's been for basically ever. Fragmentation happens when some files later get deleted and the gaps get filled by new ones that don't quite fit and have to be... well fragmented where there is space.

Edited April 9Apr 9 by Kilrah

Cool. Didn't know that was the case when writing a lot of files to a new or cleared drive. While I believe 100% what you wrote, not sure why when I wrote 30% to my drive, disconnected from Unraid, hooked to my PC and Windows found fragmentation.